Dropper and stirrer dispensing a single drop

ABSTRACT

A disposable (i.e., single-use) dropper for delivering a single drop of liquid, e.g., blood plasma or serum to, and distributing the drop of liquid over a (predetermined) area of, a substrate. The article comprises a tube formed of resilient, essentially non-plasticized, plastic material having hydrophobic properties, and being inert with respect to the liquid being dispensed. One end of the tube is open and clearly cut at right angles to the major axis of the tube, while the opposite end is closed and collapsed for a distance of about a half-inch or less from its terminus. The collapsed portion of the tube is formed as a paddle-like stirrer.

7 United States Patent 1191 1111 3,811,603 Felton May 21, 1974 [54] DROPPER AND STIRRER DISPENSING A 2,876,774 3/1959 Krantz et 111. 128/253 SINGLE DROP 3,006,386 10/1961 Greis 222/215 X 3,128,920 4/1964 Volckening et a1 222/215 [75] Inventor: Lloyd Crosser o cockeysvllle, 3,194,237 7/1965 Rubin 128/253 Md. 3,308,898 3/1967 Allen et a1. 222/214 X [73] Assignee: Hynson, Westcott Dunning, FOREIGN PATENTS OR APPLICATIONS lncmpolatedi Baltlmore 1,324,126 3/1963 France 128/2 B [22] Filed: Apr. 15, 1968 Primary Examiner-Stanley H. Tollberg [21] Appl' 72l299 Assistant Examiner-Norman L. Stack, Jr.

Attorney, Agent, or Firm-Pierce, Scheffler and [52] U.S. Cl. 222/420 Parker [51] Int. Cl B65d 47/18 [58] Field of Search 222/420, 444, 192, 191, 222/490, 214, 215, 416; 401/195, 52; [57] ABSTRACT 128/172, 28, 260, 2, 253, 307, 304, 261; A disposable (i.e., single-use) dropper for delivering a g 206/634; 239/538 single drop of liquid, e.g., blood plasma or serum to, and distributing the drop of liquid over a (predeter- [56] References Cited mined) area of, a substrate. The article comprises a UNITED STATES PATENTS tube formed of resilient, essentially non-plasticized, 917 442 4,1909 Hutchinson 222014 plastic material having hydrophobic properties, and 1 632686 6/1927 wiih combe i.:IIII IIII 128/267 being with respect quid being dispensed- 116721816 1 6/1928 Kohl 128/304 one end of the tube is p and Clearly Cut at right 2.l29,627 9/1938 Sands et a1 128/261 x ang t th aj r ax of h tube. hile th pposite 2,146,472 2/1939 HeintZ et al. 128/261 end is closed and collapsed for a distance of about a 2.428.577 9/1947 Mathis 22/2 half-inch or less from its terminus. The collapsed por- 2.579.718 12/1951 222/2|5 tion of the tube is formed as a paddle-like stirrer. 2,656,070 10/1953 222/191 X 2,770,399 1 H1956 222/215 X 4 Claims, 5 Drawing Figures 1 DROPPER AND STIRRER DISPENSING A SINGLE DROP This invention relates to the type of dispenser popularly known as a medicine dropper, and is concerned with the provision of a dispensable combined dropper and stirrer for delivering a single drop ofliquid, e.g., blood plasma, blood serum or water, and for distributing the so-delivered drop of liquid over a predetermined area of substrate.

In its preferred embodiment, the invention consists in a disposable, single drop, dispenser-stirrer for use in conjunction with the carrying out of serological tests employing a standard test card'such for example as that of the RPR card test described and claimed in U.S. Pat. No. 3,072,319, John H. Brewer.

Dispensing a single drop of liquid from a hand-held pipette is not easy. When using a pipette there exists the danger of inadvertently delivering a plurality of drops where a single drop is all that should be dispensed. The same is true with regard to use of the conventional medicine dropper equipped with a rubber bulb for creating the partial vacuum necessary to draw a supply of liquid into the chamber of the dropper. Neither the conventional pipette nor the conventional medicine dropper constitutes an economically feasible one-use" disposable article.

For delivering a single drop of plasma or serum to the test area of a test card such as the above mentioned RPR card, it heretofore had been conventional to'use a glass capillary tube equipped with a rubber bulb for sucking liquid into the capillary. By skilled use of this device it was possible to draw up a small amount of plasma or serum from a blood collecting tube and to deliver a single drop of the liquid to a test spot, whereupon the liquid drop could be distributed over the area of the test spot by stirring it about with a conventional flat-ended toothpick. The rubber bulb could then be drawn off of the used capillary tube and used toothpick could be discarded.

The length of the glass capillary tube was determined by the internal diameter of tubing. For one particular diameter of glass tubing so used, the 0.05 ml capillary is 2 )6 inches long, and when it'is half-filled (to a line marked on the glass), the volume delivered is approximately 0.05 ml.

It has now been'found that the above-described combination of re-usable rubber bulb, one-use glass capillary tube and one-use toothpick may be supplanted by the simple, one-piece, accurate, disposable combined dropper-and stirrer about to be described. The article is inert to blood, blood plasma, blood serum and water; it accurately delivers a single drop of liquid to a test spot, and the drop so delivered is of accurately controlled size. A part of the same article is uniquely adapted for use in spreading such a delivered drop of liquid over the area of the test spot, usually a circular area outlined by a colored peripheral line.

In particular, the one-piece article is formed from a tube of resilient, essentially unplasticized, plastic material having hydrophobic properties and being inert to blood or other liquid to be dispensed thereby. One end of the tube is open and is cleanly cut at right angles to the major axis of the tube. It is this open ended part of the tubular piece which constitutes the dropper of the combined dropper-stirrer article. The opposite end is closed, being sealed shut a short distance (e.g., twothirds to one-third of an inch) from the terminus of the tubular piece; the sealed flat end portion, which may lie in the same plane as that in which lies the major axis of the tube, constitutes a paddle-like stirrer for distributing a drop of liquid which has been provided through use of the remote end of the combined dropper-stirrer article.

As mentioned above, the tube is formed, by extrusion, from a resilient, hydrophobic, essentially unplasticized plastic material. Preferably, the specific plastic material used in forming the aforesaid tube is pure virgin polypropylene, but other plastic materials, such for example as polyethylene, and even polyethylenecoated paper, have been found to be operable. Relatively hydrophyllic materials, such for example as cellulose acetate or polyvinyl chloride or polyvinyl acetate, are least desirable. The plastic material should be transparent and may be lightly colored or be colorless. The tube has an internal diameter and a wall thickness which in conjunction with the resiliency of the material itself conspire to make the tube readily squeezed shut by pressure between a thumb and a forefinger of a technician and to promptly return to original tubular cross-sectional configuration when pressure on opposite sides thereof is released. In the case of one specific formulation of polypropylene, the tube formed therefrom is 5.0 inches in length and has an internal diameter of 0.152 1 0.0025 inch and a wall thickness of 0.0065 i 0.0005 inch, and is adapted to dispense a volume of approximately 0.05 ml. of plasma or serum.

The stirrer may pick up (i.e., retain on its surface) a minimal amount, e.g., 0.002 0.005 gram, of the test liquid. In this connection, it is noted that in a case where the tube is formed from a relatively hydrophyllic plastic material the stirrer retains a relatively large, but varying, amount of the test liquid and hence interferes with the accuracy of the test.

The important criterion of being capable of dispensing the correct volume of liquid is, in the case under consideration, dependent not only on the wall thickness and internal diameter of the tube and on its resiliency, but also on a clean cut of the open end of the tube at right angles to the axis of the tube. The dropper, when held vertically, delivers a drop having a volume of 0.04 0.06 milliliters, preferably 0.045 0.055 ml., of blood plasma. By reason of the hydrophobicity of the polypropylene, only a very small amount of liquid is retained on the wall of the dropper when the required single drop has been discharged therefrom; it is very difficult if not impossible to express a second drop from the dropper in any one filling.

The reproducibility of drop size delivered by the dropper-stirrer article of the present invention is graphically shown in FIG. 5 of the accompanying drawing in which the drop weights from 877 randomly selected dropper-stirrer articles are plotted, the abscissae representing drop weights and the ordinates representing numbers of the droppers delivering the designated drop weights.

In use, the dropper is compressed between thumb and forefinger of the technician, about 1 or 2 inches from its sealed end, and is squeezed shut while it is lowered (open end down) into a vertically held bloodcollecting tube and the open end immersed in a pool of liquid (e.g., blood plasma) in the lower end of the liquid specimen in the blood-collecting tube. Then, release of pressure on the wall of the dropper creates a sub-atmospheric pressure within the dropper sufficient to draw into the dropper slightly in excess of a single drop of the liquid under test. The dropper is then withdrawn from the collecting tube and is held vertically (open end down) over (but spaced from) a designated test area on a test card, and one drop of test liquid is expressed from the dropper onto such test area by suitably squeezing the control portion of the dropper. Thereupon, the technician turns the dropper about in his hand and, with the paddle-like sealed end of the article, he distributes the drop over the test area. Thereafter, the dropper-stirrer article is discarded.

The invention will now be further described with reference to the appended drawing, in which FIG. 1 is a top plan view of one embodiment of the dropper-stirrer article of the present invention;

FIG. 2 is a side elevational view of the article shown in FIG. 1;

FIG. 3 is a top plan view of a modified form of the article;

FIG. 4 is an enlarged sectional view of the stirrer end of the article, showing the collapsed and sealed walls of the tubular article; and

FIG. 5 is a graph which, as above stated, represents the drop weight reproducibility of 877 randomly selected dropper-stirrer articles of the present invention, in which graph the abscissae represent drop weights (of blood plasma) in ten-thousandths of a gram and the ordinants represent number of articles delivering drops of identical weight, each horizontal representing tens of articles.

Reproducibility tests were conducted with blood plasma, in which relation weight in grams is almost exactly equivalent to volumne in milliliters.

In FIG. I, the numeral represents a tubular piece, having a length of 5 inches and formed by extrusion from virgin polypropylene. The internal diameter ID. is 0.152 t 0.0025 inch and the standard wall thickness W.T. is 0.0065 inch. At about three-eigths inch from one end the tubular piece has been collapsed and heat sealed shut as indicated at 11 and 12, the terminus of the piece having been die cut in a semi-circular form as shown at 13. The collapsed and sealed portion 11, 12 which constitutes the paddle-like stirrer part of the article, may, as shown in FIG. 2, be in the plane of the major axis of the tube; or, the collapsed and sealed portion may be bent a few degrees to one side or the other from the major axis of the tube (alternative not shown in the drawing).

In the embodiment shown in FIG. 3, the terminus 14 of the collapsed and sealed portion l1, 12 is die cut in the form of a paddle end having a width somewhat less than that of portion 12.

FIG. 4 shows in greater detail, a cross-sectional, enlarged, view of the upper part of the dropper-stirrer, the collapsed and sealed upper end of the tube 10 being indicated at 11, 12 and the wall thickness (WT) and internal diameter (I.D.) being indicated.

FIG. 5 graphically illustrates the remarkable reproducibility of the single drops delivered by a large number (877) of randomly selected dropper-stirrers of the present invention. As shown in FIG. 5, out of this number, approximately 847, i.e., about 96.5 percent, delivered drops varying by not more than 0.005 gram from the median weight of 0.0551 gram. This remarkable uniformity is of real importance in the case of dispensing a very small volume of a medicament or a chemical reagent or of a blood plasma (or, serum) sample.

In use, the dropper-stirrer is grasped, at about its midpoint or above and squeezed shut, between thumb and forefinger of the operator, who, without releasing pressure, introduces the open (lower) end of the device into a blood-collecting tube and immerses the open end in a pool of liquid test material (plasma, or serum): then, while holding the end of the device immersed the operator releases pressure on the dropper-stirrer, thereby drawing up into the tube an amount of the test liquid somewhat in excess of the one drop. He then holds the device vertical and close to but spaced from a test spot on a test card, and squeezes the tube so as to express one drop of test liquid onto the test spot. Reversing the device in his hand, the operator manipulates the drop of liquid, with the stirrer end of the device, so as to cover the area of the marked test spot. The device is then discarded. In the instance of making an RPR card test, the operator observes visual change (if any) in the so spread liquid, and records his observation.

I claim:

1. A disposable liquid dispensing and spreading device for delivering a single drop of liquid of accurate volume to a substrate and for spreading the so dispensed drop of liquid over an area of such substrate, which device consists of a unitary cylindrical tube having a uniform wall thickness throughout and formed of a resilient transparent plastic material which is inert to and substantially hydrophobic towards the liquid to be dispensed, which tube is collapsed and sealed shut for a short distance at one end thereof and shaped to facilitate the spreading of a dispensed drop of liquid over a predetermined area of substrate, and is open at its opposite end, the wall of the tube being at its open end cleanly cut across at right angles to the major axis of the tube, said open end part of the tube providing a dropper so sized, in relation to the viscosity of the liquid to be dispensed, that when the empty tube is squeezed shut intermediate its ends by compression a thumb and a finger and the open end dipped into a body of the liquid to be dispensed and then the pressure released so as to create a sub-atmospheric pressure within the tube sufficient to draw into the tube slightly in excess of a single drop of the liquid to be dispensed, and, when the tube has then been withdrawn from the body of liquid and held vertically over a test area and the tube again is squeezed between thumb and finger one single drop of the liquid can be dispensed from the tube.

2. A disposable liquid dispensing device for delivering a single drop of liquid of accurate volume, said dropper consisting of a unitary cylindrical tube having a uniform wall thickness throughout and formed of a resilient material which is inert to and substantially hydrophobic towards the liquid to be dispensed, which tube is collapsed and sealed shut for a short distance at one end thereof, and is open at its opposite end, the wall of the tube being at its open end cleanly cut across at right angles to the major axis of the tube, said open end part of the tube providing a dropper so sized, in relation to the viscosity of the liquid to be dispensed, that when the empty tube is squeezed shut intermediate its ends by compression between a thumb and a finger and the open end dipped into a body of the liquid to be dispensed and then the pressure released so as to create ene and has a length of from 4 to 8 inches and an internal diameter of 0.152 t 0.0025 inch and a wall thickness of 0.0065 i 0.0005 inch and delivers a single serum drop of 0.05 ml i 0.0l.

4. The dispensing device defined in claim 3, wherein the collapsed and closed portion of the tube has a length of from one-half to one inch and is shaped to constitute a spreader element. 

1. A disposable liquid dispensing and spreading device for delivering a single drop of liquid of accurate volume to a substrate and for spreading the so dispensed drop of liquid over an area of such substrate, which device consists of a unitary cylindrical tube having a uniform wall thickness throughout and formed of a resilient transparent plastic material which is inert to and substantially hydrophobic towards the liquid to be dispensed, which tube is collapsed and sealed shut for a short distance at one end thereof and shaped to facilitate the spreading of a dispensed drop of liquid over a predetermined area of substrate, and is open at its opposite end, the wall of the tube being at its open end cleanly cut across at right angles to the major axis of the tube, said open end part of the tube providing a dropper so sized, in relation to the viscosity of the liquid to be dispensed, that when the empty tube is squeezed shut intermediate its ends by compression a thumb and a finger and the open end dipped into a body of the liquid to be dispensed and then the pressure released so as to create a sub-atmospheric pressure within the tube sufficient to draw into the tube slightly in excess of a single drop of the liquid to be dispensed, and, when the tube has then been withdrawn from the body of liquid and held vertically over a test area and the tube again is squeezed between thumb and finger one single drop of the liquid can be dispensed from the tube.
 2. A disposable liquid dispensing device for delivering a single drop of liquid of accurate volume, said dropper consisting of a unitary cylindrical tube having a uniform wall thickness throughout and formed of a resilient material which is inert to and substantially hydrophobic towards the liquid to be dispensed, which tube is collapsed and sealed shut for a short distance at one end thereof, and is open at its opposite end, the wall of the tube being at its open end cleanly cut across at right angles to the major axis of the tube, said open end part of the tube providing a dropper so sized, in relation to the viscosity of the liquid to be dispensed, that when the empty tube is squeezed shut intermediate its ends by compression between a thumb and a finger and the open end dipped into a body of the liquid to be dispensed and then the pressure released so as to create a sub-atmospheric pressure within the tube sufficient to draw into the tube slightly in excess of a single drop of the liquid to be dispensed, and, when the tube has then been withdrawn from the body of liquid and held vertically over a test area and the tube again is squeezed between thumb and finger one single drop of the liquiD can be dispensed from the tube.
 3. The disposable, single-drop, liquid-dispensing device defined in claim 2 further characterized in that said tube is formed of resilient transparent polypropylene and has a length of from 4 to 8 inches and an internal diameter of 0.152 + or - 0.0025 inch and a wall thickness of 0.0065 + or - 0.0005 inch and delivers a single serum drop of 0.05 ml + or - 0.01.
 4. The dispensing device defined in claim 3, wherein the collapsed and closed portion of the tube has a length of from one-half to one inch and is shaped to constitute a spreader element. 